prolog './g620.ijs'
NB. @ -------------------------------------------------------------------

({.x|.y) -: (x=:?20) {.@|. y=:?20 3$1000

1 -: 0 1 (-~/@[) 1

'domain error' -: ". etx '3 @ 3'
'domain error' -: ". etx '3 @ +'
 6 -: +:@3 ''
 6 -: '' +:@3 ''
_ _ _ -: +:@3 b. 0




epilog''

